AN airborne race car smashed into a fence, injuring spectators, during a horrific multi-car smash in the final moments of a NASCAR race in the US.

The frightening, fiery crash that sent Kyle Larson's car airborne and debris spinning into the stands injured dozens of race fans at the NASCAR stock car Nationwide Series season-opener at Daytona.

Joie Chitwood, president of Daytona International Speedway, said 14 injured fans had been transported from the circuit for treatment at local hospitals and 14 more were treated at the track's medical facility.

"It's not appropriate for me to comment on that,'' Chitwood said in a press conference held at the circuit some three hours after the wreck.

Various media reports put the number of injured at more than 30, with ESPN reporting that one adult had life-threatening head trauma and a 14-year-old was in critical but not life-threatening condition in hospital.

The wreck, which occurred almost as Tony Stewart was taking the chequered flag for victory, began when race leader Regan Smith turned sideways and a dozen cars bunched behind him.

"My fault,'' admitted Smith. "I threw a block.''

Kyle Larson (32) is airborne after a multi-car crash, including Parker Kligerman (77), Justin Allgaier (31) and Brian Scott (2) during the final lap of the NASCAR Nationwide Series auto race at Daytona.Source: AP

Larson, a Japanese-American driver who was making his first start in NASCAR's second-tier series, was launched into the catch-fencing.

"I was getting pushed from behind, and by the time my spotter said, 'Lift,'' it was too late,'' said Larson, who was able to climb out of what remained of his vehicle.

"I had some flames come in the cockpit. I was all right and could get out of the car quickly. It was definitely a big hit.''

Larson's car tore a hole in the fence separating the track from the stands. His engine sheared off with at least one tire and other debris flying into the grandstand.

"I looked in the mirror and that's the worst image I've ever seen in a race in my life,'' Stewart said.

Kyle Larson's car is on fire as he slides down the track with Regan Smith after being involved in a crash at the conclusion of the NASCAR Nationwide Series race at Daytona.Source: AP

A fan who identified himself as "Tyler Andersen'' sent amateur video to ESPN and spoke with the sports network about the scary scene.

"I saw a tire about 10 feet from me, just a row above me with a man under it and people yelling for help,'' he said in a telephone interview.

"Our prayers and thoughts are with everybody they are working on,'' NASCAR President Mike Helton said of those being treated by medical personnel.

None of the drivers involved in the crash was injured, but driver Michael Annett was brought to hospital with chest bruising after hitting a safety barrier in an earlier crash in the race.

"We've always known since racing started this is a dangerous sport,'' a subdued Stewart said. "As much as we want to celebrate, I'm more concerned about the fans and the drivers right now.''

Kyle Larson climbs out of his car after being involved in a crash at the conclusion of the NASCAR Nationwide Series race at Daytona.Source: AP

Chitwood said speedway and NASCAR officials responded appropriately and according to their safety protocols, with emergency personnel in place and able to begin work promptly.

Steve O'Donnell, NASCAR's senior vice president for racing operations, said the entire incident would be reviewed to see what, if any, changes could be made to improve safety.

Until then he declined to speculate on what went wrong or right.

"We need to take the time to really study it and see what we can improve on,'' O'Donnell said.

The race came on the eve of the season-opening event in NASCAR's top-flight Sprint Cup series, the Daytona 500.

Medical personnel assist fans sitting close to the wall following an incident at the finish of a NASCAR Nationwide Series race at Daytona.Source: Getty Images

Both O'Donnell and Chitwood said they expected Sunday's race to start on schedule.

"We expect to go racing tomorrow with no changes,'' Chitwood said.

Danica Patrick will start the Daytona 500 from pole position after becoming the first woman to top qualifying for a NASCAR race.

Patrick had also picked up a ride for Saturday's race, driving for Turner Scott Motorsports. She suffered engine failure early on and wasn't involved in the late-race chaos.

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